1. Field of the Invention
A dual function fastener and method of use is disclosed.
2. Discussion of the Background
Pin-type fasteners with removable pintails are, in general, well known. In use of the fastener, the pintail is gripped by a first part (e.g. in the form of a set of jaws) of an installation tool, a second part (e.g. in the form of an annular anvil) of the tool engages a second part of the fastener (e.g. in the form of a collar or shell), and the tool is activated (e.g. by hydraulic power) to retract the first part of the tool relative to the second part of the tool, thereby to cause the second part of the tool to deform one or both parts of the fastener.
The effect of such deformation may be to clamp two or more workpieces together, and/or to secure one or the other or both parts of the fastener to a workpiece, and/or to lock the two parts of the fastener to each other, depending upon the design of the fastener.
After such locking engagement has been achieved, it is usually necessary to remove the pintail because it protrudes beyond the second part of the installed fastener. However, such removal can be made to serve the useful function of ensuring that sufficient force has been applied to the fastener by the tool to achieve satisfactory deformation. This is arranged by taking the reaction to the deforming load as tension load on the pintail, and by designing and manufacturing the pin so that it fractures at a tension load of a predetermined value, or of not less than a minimum predetermined value.
The pin is alternatively known as a stem, and such fasteners are also known as breakstem fasteners.
Various examples of such fasteners are described in patent specifications GB 424241, GB 629098 (commercially available under the trademark AVDELOK), GB 1 029 654 (commercially available under the trademark AVEX), GB 1538872 (commercially available under the trademark MONOBOLT), and GB 2227538 (commercially available under the trademark MAXLOK).
As explained in GB 424241 at page 3 lines 119 to 128, the locking grooves on the pin could be of spiral (or rather helical) form so as to provide a screwthread, so that the two parts of the installed fastener can later be unscrewed apart.
There are many different varieties of pin-type fasteners with removable pintails, of which the abovementioned references illustrate some of the more important ones.
Patent specifications GB 1528730 and GB 1593508 disclose the attachment of various varieties of pin-type fasteners to a workpiece by means of so-called flash-butt welding or stud welding, so that the fastener does not protrude through the first workpiece, and a second workpiece may be then secured to the first workpiece by means of the pin-type fastener.
It is also known to electrically weld a simple stud to a metal workpiece, i.e. the so-called stud welding process. This is described in GB 1528730 at page 1 lines 8 to 16.
In all cases, when the pin-type fastener is installed, the pintail is broken off and is of no further use. At best, broken off pintails are collected and used as scrap metal i.e. to be melted down to provide metal for reprocessing.